Wash water-circulating apparatus for washing machines and method of controlling the same

ABSTRACT

Disclosed herein are a wash water-circulating apparatus for washing machines and a method of controlling the same. The wash water-circulating apparatus comprises a circulation channel connected between one side of a tub and the other side of the tub for allowing wash water to circulate therethrough, a pump assembly disposed on the circulation channel for forcibly circulating the wash water, and a water level sensor disposed at the pump assembly or on the circulation channel downstream of the pump assembly for measuring the water pressure of the wash water discharged from the pump assembly. According to the present invention, the minimum amount of the wash water necessary for the pump operation is used when the washing and rinsing processes are carried out, whereby the consumed amount of the wash water is decreased, and the operational reliability of the pump is improved.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a washing machine, including adrum washing machine, and more particularly to a wash water-circulatingapparatus for washing machines, which is capable of circulating/sprayingwash water in a tub so that washing and rinsing operations are carriedout. The present invention also relates to a method of controlling sucha wash water-circulating apparatus for washing machines.

[0003] 2. Description of the Related Art

[0004]FIG. 1 is a perspective view of a conventional washing machine,especially a conventional drum washing machine.

[0005] As shown in FIG. 1, the conventional drum washing machinecomprises: a casing 2 forming the exterior of the drum washing machine;a tub 6 disposed in the casing 2 in such a manner that the upper end ofthe tub 6 is suspended by means of a spring 4, and simultaneously thelower end of the tub 6 is supported by means of a damper assembly (notshown); a drum 8 rotatably mounted in the tub 6 for washing, rinsing anddrying clothes; a motor 10 mounted at the rear of the tub 6, in such amanner that the motor 10 is connected to the drum 8, for rotating thedrum 8; a heater 12 mounted to the lower part of the tub 6 for heatingwash water; and a pump assembly 20 including a pump connected to thelower part of the tub 6 by means of a drainage bellows 14 for pumpingwash water so that the wash water is circulated or draining the washwater to the outside.

[0006] The heater 12 is disposed between the tub 6 and the drum 8. Thetub 6 includes a heater mounting part 6 a formed at the lower endthereof. The heater mounting part 6 a of the tub 6 is downwardlyextended from the tub 6 so that the heater 12 is mounted in the heatermounting part 6 a.

[0007] Above the tub 6 are mounted a water-supply valve assembly 16 forsupplying wash water into the tub 6 and a detergent box assembly 18 forsupplying a detergent into the tub 6.

[0008] To the drainage bellows 14 is mounted a water level sensor fordetecting the water pressure of the wash water flowing to the pumpassembly 20, whereby the water level of the wash water in the tub 6 isdetected.

[0009] To the pump assembly 20 is connected a circulation channel 24 forcirculating the wash water to the tub. To the pump assembly 20 is alsoconnected a drainage channel 26 for draining the wash water.

[0010] The circulation channel 24 has one end connected to the pumpassembly 20 and the other end disposed in a gasket 7, which is mountedbetween the tub 6 and the casing 2 for preventing leakage of the washwater. Specifically, the other end of the circulation channel 24 isdisposed in the inner upper part of the gasket 7 so that the wash wateris sprayed to the upper part of the tub 6.

[0011] When the wash water is pumped on the basis of the operatingcondition of the pump assembly 20, therefore, the wash water is suppliedto the upper part of the tub 6 along the circulation channel 24.Consequently, the clothes are rapidly wetted, whereby the washingefficiency of the drum washing machine is improved. Furthermore, thewater level of wash water to be supplied is lowered when the clothes arerinsed, whereby the amount of consumed wash water is reduced.

[0012] Now, a description will be given of a water level based onwater-supplying time and a pump operating condition of the drum washingmachine with the above-stated construction when water is supplied withreference to FIG. 2.

[0013] When the water supply valve is opened, wash water is supplied. Asthe wash water is supplied, the water level of the wash water in the tub6 is gradually increased throughout the tub 6. As the motor 10 isoperated, the drum 8 is rotated in the forward/reverse direction so thatthe clothes in the drum 8 are moved so that the clothes become wet.Consequently, the water level of the wash water is repeatedlyincreased/decreased.

[0014] In the case that the appropriate amount of the wash water issupplied into the tub 6, the motor 10 is operated so that the drum 8 isrotated. Consequently, a washing process is carried out. Simultaneously,the pump is operated so that the wash water at the lower part of the tub6 is sprayed to the upper part of the tub 6. In this way, the washingoperation is carried out.

[0015] When the motor 10 and the pump are operated for washing theclothes and circulating the wash water after the prescribed amount ofthe wash water is supplied into the tub 6, the clothes become wet.Simultaneously, the pump is operated so that the wash water isintroduced into the circulation channel 24. As a result, the wash waterin the tub 6 is considerably decreased.

[0016] However, when the wash water is not sufficiently supplied to thetub 6 in the conventional drum washing machine as described above, andtherefore when wash water in the tub is insufficient in the course of are-circulation washing process using the circulation channel, air may beintroduced into the pump along with the wash water. As a result, thewash water re-circulation washing process is not normally carried out.

[0017] Although the water level sensor 22 is disposed on the inletchannel of the pump, the water level of the wash water in the tub is notexactly detected when the wash water re-circulation washing process iscarried out since the moved amount of the wash water is increased.Consequently, it is required that an excessive amount of wash water besupplied so that the heater 12 is always operated while being submergedunder the wash water. Even when the rinsing process, which requires nooperation of the heater, is carried out, it is required that theappropriate water level of the wash water be maintained so that the pumpis normally operated. As a result, it is required that an excessiveamount of the wash water be supplied considering the flow of the washwater.

[0018] Consequently, the washing process is carried out while more washwater is supplied to the tub than is necessary so that the heater 12 andthe pump are normally operated with the result that the consumed amountof the wash water is increased, and the consumed amount of electricenergy is also increased.

SUMMARY OF THE INVENTION

[0019] Therefore, the present invention has been made in view of theabove problems, and it is an object of the present invention to providea wash water-circulating apparatus for washing machines, wherein a waterlevel sensor is disposed at the outlet port of a pump to exactlydetermine whether the pump is normally operated or not, whereby thereliability of a wash water re-circulation washing process is improved.

[0020] It is another object of the present invention to provide a methodof controlling the above-mentioned wash water-circulating apparatus forwashing machines.

[0021] It is another object of the present invention to provide a washwater-circulating apparatus for washing machines, wherein a water levelsensor and a heater are disposed at the outlet port of a pump to carryout a washing process with the minimum amount of wash water necessaryfor normal operations of the heater and the pump, whereby the consumedamount of the wash water is decreased and the consumed amount ofelectric energy is also decreased.

[0022] It is still another object of the present invention to provide amethod of controlling the above-mentioned wash water-circulatingapparatus for washing machines.

[0023] In accordance with one aspect of the present invention, the aboveand other objects can be accomplished by the provision of a washwater-circulating apparatus for washing machines, comprising: acirculation channel connected between one side of a tub and the otherside of the tub for allowing wash water to circulate therethrough; apump assembly disposed on the circulation channel for forciblycirculating the wash water; and a water level sensor disposed at thepump assembly or on the circulation channel downstream of the pumpassembly for measuring the water pressure of the wash water dischargedfrom the pump assembly.

[0024] Preferably, the apparatus further comprises a heater assemblydisposed on the circulation channel downstream of the pump assembly forheating the circulated wash water.

[0025] The water level sensor is mounted on the circulation channelbetween the pump assembly and the heater assembly, at the heaterassembly, or on the circulation channel downstream of the heaterassembly.

[0026] Preferably, the apparatus further comprises a drainage channelconnected to the pump assembly for discharging the wash water in the tubto the outside, wherein the wash water is selectively pumped to thecirculation channel or to the drainage channel by means of the pumpassembly.

[0027] The circulation channel has a wash water-spraying end disposed atthe lower part of the tub or at the upper part of the tub so that thewash water is sprayed into the tub through the wash water-spraying end.

[0028] In accordance with another aspect of the present invention, thereis provided a washing machine comprising: a tub for storing wash water;a circulation channel connected between one side of the tub and theother side of the tub for allowing the wash water to circulate into thetub therethrough so that the wash water is sprayed into the tub; a pumpassembly disposed on the circulation channel for forcibly circulatingthe wash water; a water level sensor for measuring the water pressure ofthe wash water discharged from the pump assembly; and control means forcontrolling supply of the wash water into the tub and operation of thepump assembly on the basis of the signal from the water level sensor.

[0029] Preferably, the machine further comprises a drainage channelconnected to the pump assembly for discharging the wash water in the tubto the outside, wherein the wash water is selectively pumped to thecirculation channel or to the drainage channel by means of the pumpassembly.

[0030] The machine may be a drum washing machine with the tub disposedapproximately horizontally or an upright washing machine with the tubdisposed approximately vertically.

[0031] In accordance with still another aspect of the present invention,there is provided a method of controlling wash water circulation forwashing machines, comprising the steps of: re-circulating wash watersupplied into a tub along a circulation channel by operating a pump; andmeasuring the discharging pressure of the pump while the wash water isre-circulated, and further supplying water into the tub if thedischarging pressure of the pump is less than a prescribed pressure.

[0032] The pump is stopped for a prescribed period of time when thewater is further supplied into the tub.

[0033] The pump is periodically stopped/operated when the water isfurther supplied into the tub.

[0034] The pump-stopping time is shorter than the pump-operating time.

[0035] Preferably, the method further comprises the steps of measuringthe discharging pressure of the pump after the water is furthersupplied, and stopping supply of water if the discharging pressure ofthe pump is not less than a prescribed pressure.

[0036] With the wash water-circulating apparatus for washing machines asmentioned above, it is possible to detect the water pressure of the washwater discharged from the pump assembly operated when the wash water isre-circulated so that it is determined whether the pump is normallyoperated or not and the wash water supplied into the tub is detected.Consequently, the minimum amount of the wash water necessary for thepump operation is used when the washing and rinsing processes arecarried out, whereby the consumed amount of the wash water is decreased,and the operational reliability of the pump is improved.

[0037] With the method of controlling wash water circulation for washingmachines as mentioned above, the wash water is further supplied into thetub, and simultaneously the pump is repeatedly stopped for a prescribedtime while the pump is operated so that air introduced into the pump isdischarged, whereby the operational reliability of the pump is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other objects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

[0039]FIG. 1 is a side view, in cross section, of a conventional drumwashing machine;

[0040]FIG. 2 is a graph illustrating a water level based onwater-supplying time and a pump operating condition of the conventionaldrum washing machine;

[0041]FIG. 3 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a firstpreferred embodiment of the present invention;

[0042]FIG. 4 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a secondpreferred embodiment of the present invention;

[0043]FIG. 5 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a thirdpreferred embodiment of the present invention;

[0044]FIG. 6 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a fourthpreferred embodiment of the present invention;

[0045]FIG. 7 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a fifthpreferred embodiment of the present invention;

[0046]FIG. 8 is a flow chart illustrating a method of controlling a drumwashing machine provided with a wash water-circulating apparatusaccording to the present invention; and

[0047]FIG. 9 is a graph illustrating a water level based onwater-supplying time and a pump operating condition of a drum washingmachine provided with a wash water-circulating apparatus according tothe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Now, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

[0049]FIG. 3 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a firstpreferred embodiment of the present invention.

[0050] As shown in FIG. 3, the drum washing machine according to thefirst preferred embodiment of the present invention comprises: a casing52 forming the exterior of the drum washing machine; a tub 56 disposedin the casing 52 in such a manner that the upper end of the tub 56 issuspended by means of a spring 54, and simultaneously the lower end ofthe tub 56 is elastically supported by means of a damper assembly (notshown); a drum 58 rotatably mounted in the tub 56 for washing, rinsingand drying clothes; a motor 60 mounted at the rear of the tub 56, insuch a manner that the motor 60 is connected to the drum 58, forrotating the drum 58; a heater 62 mounted to the lower part of the tub56 for heating wash water; and a pump assembly 70 including a pumpconnected to the lower part of the tub 56 by means of a drainage bellows64 for pumping or draining the wash water; a circulation channel 74having one end connected to the pump assembly 70 and the other enddisposed in the tub 56 for spraying the wash water pumped by means ofthe pump assembly 70 so that the wash water is circulated to the tub 56;and a water level sensor 72 disposed on the circulation channel 74 fordetecting the water level of the wash water in the tub 56 by measurementof the water pressure of the wash water discharged from the pumpassembly 70.

[0051] Above the tub 56 are mounted a water-supply valve assembly 66including a water-supply valve (not shown) for supplying wash water intothe tub 56 and a detergent box assembly 68 for supplying a detergentinto the tub 56.

[0052] The heater 62 is disposed in a heater mounting part 56 a formedat the lower part of the tub 56. The heater mounting part 56 a of thetub 56 is downwardly extended from the tub 56 so that the heater 62 ismounted in the heater mounting part 56 a.

[0053] The circulation channel 74 is connected to the pump assembly 70for pumping the wash water from the tub 56. To the pump assembly 70 isalso connected a drainage channel 76 for draining the wash water fromthe tub 56.

[0054] One end 74 a of the circulation channel 74 is connected to thepump assembly 70, and the other end 74 b of the circulation channel 74is disposed in a gasket 57, which is mounted between the front end ofthe tub 56 and the casing 52 for preventing leakage of the wash water.The end 74 b of the circulation channel 74 is formed in the shape of anozzle for spraying the wash water.

[0055] The water level sensor 72 is disposed on the circulation channel74 downstream of the pump assembly 70 for measuring the water pressureof the wash water having passed through the pump. Consequently, it canbe determined whether the pump is normally operated, and therefore thewater level can be controlled more accurately.

[0056] When it is detected that the water pressure is lower than aprescribed pressure as air is introduced into the pump along with thewash water, the pump is not normally operated. Consequently, the waterlevel sensor 72 determines that the appropriate amount of wash water isnot supplied into the tub 56. When it is detected that the waterpressure is higher than the prescribed pressure as only the wash wateris introduced into the pump, the pump is normally operated.Consequently, the water level sensor 72 determines that the appropriateamount of wash water is supplied into the tub 56, and controls theoperation of the water-supply valve.

[0057] In the case that the prescribed pressure of the water levelsensor 72 is properly controlled, therefore, the heater 62 is submergedunder the wash water in the tub 56, and the appropriate water level ofthe wash water necessary for normal operation of the pump is maintained,whereby the consumed amount of the wash water is decreased, and theconsumed amount of electric energy is also decreased.

[0058]FIG. 4 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a secondpreferred embodiment of the present invention. The drum washing machineprovided with the wash water-circulating apparatus according to thesecond preferred embodiment of the present invention is similar to thedrum washing machine provided with the wash water-circulating apparatusaccording to the first preferred embodiment of the present inventionexcept that the water level sensor 72 is disposed at one side of thepump assembly to detect the water pressure of the wash water dischargedfrom the pump.

[0059] Specifically, the pump assembly 70 includes a pump case having aninlet port, through which the wash water is introduced, and an outletport, through which the wash water is discharged. The pump is mounted inthe pump case. The water level sensor 72 is mounted to one side of thepump case in such a manner that the water level sensor 72 communicateswith the pump case. The water level sensor 72 determines whether thepump is operated or not and the water level of the wash water in the tub56 by measurement of the water pressure of the wash water passingthrough the pump assembly 70.

[0060]FIG. 5 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a thirdpreferred embodiment of the present invention.

[0061] As shown in FIG. 5, the drum washing machine according to thethird preferred embodiment of the present invention comprises: a casing82 forming the exterior of the drum washing machine; a tub 86 disposedin the casing 82 in such a manner that the upper end of the tub 86 issuspended by means of a spring 84, and simultaneously the lower end ofthe tub 86 is elastically supported by means of a damper assembly (notshown); a drum 88 rotatably mounted in the tub 86 for washing, rinsingand drying clothes; a motor 90 mounted at the rear of the tub 86, insuch a manner that the motor 90 is connected to the drum 88, forrotating the drum 88; a pump assembly 100 including a pump connected tothe lower part of the tub 86 by means of a drainage bellows 94 forpumping or draining wash water; a circulation channel 104 having one endconnected to the pump assembly 100 and the other end disposed in the tub86 for spraying wash water pumped by means of the pump assembly 100 sothat the wash water is circulated to the tub 86; a heater assembly 92disposed on the circulation channel 104 for heating wash water; and awater level sensor 102 disposed on the circulation channel 104 fordetecting the water pressure of the wash water discharged from theheater assembly 92.

[0062] The heater assembly 92 includes a heater case having an inletport, through which the wash water is introduced, and an outlet port,through which the wash water is discharged. In the heater case ismounted an electric heater. As the pump is operated, the wash waterpasses through the heater assembly 92, by which the wash water isheated.

[0063] The circulation channel 104 is connected to the pump assembly 100for pumping the wash water from the tub 86. To the pump assembly 100 isalso connected a drainage channel 106 for draining the wash water fromthe tub 86.

[0064] One end 104 a of the circulation channel 104 is connected to thepump assembly 100 and the heater assembly 92, which are disposed belowthe tub 86, and the other end 104 b of the circulation channel 104 isdisposed in the inner lower part of the tub 86 in such a manner that theother end 104 b of the circulation channel 104 is extended upward.Consequently, the circulation channel 104 is relatively shortened,whereby the flow loss is reduced, and the consumed amount of wash wateris decreased.

[0065] The water level sensor 102 is disposed on the circulation channel104 downstream of the heater assembly 92 for measuring the waterpressure of wash water discharged from the pump assembly in the casethat the pump is operated when water is supplied. Consequently, it isdetermined whether the pump is normally operated or not, and thereforethe water level of the wash water in the tub 86 is detected.

[0066] The water level of the wash water in the tub 86, which isdetected by means of the water level sensor 102, is the minimum waterlevel at which the pump can be operated.

[0067] Therefore, the water level sensor 102 detects the water level ofwater at which the pump can be operated, and stops the operation of thewater-supply valve. Consequently, the consumed amount of the wash wateris decreased, and the consumed amount of electric energy necessary foroperations of the pump and the heater is also decreased.

[0068]FIG. 6 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a fourthpreferred embodiment of the present invention. The drum washing machineprovided with the wash water-circulating apparatus according to thefourth preferred embodiment of the present invention is similar to thedrum washing machine provided with the wash water-circulating apparatusaccording to the third preferred embodiment of the present inventionexcept that the water level sensor is mounted in a different way.

[0069] Specifically, the water level sensor 102 is disposed on aconnection channel 105, which is a part of the circulation channel 104and mounted between the pump assembly 100 and the heater assembly 92,for measuring the water pressure of the wash water discharged from thepump assembly 100. Consequently, it is determined whether the pump isnormally operated or not, and the water level of the wash water in thetub 86 is detected.

[0070]FIG. 7 is a side view, in cross section, of a drum washing machineprovided with a wash water-circulating apparatus according to a fifthpreferred embodiment of the present invention. The drum washing machineprovided with the wash water-circulating apparatus according to thefifth preferred embodiment of the present invention is similar to thedrum washing machine provided with the wash water-circulating apparatusaccording to the third preferred embodiment of the present inventionexcept that the water level sensor is mounted in a different way. Thewater level sensor 102 is disposed at one side of the heater assembly 92for detecting the water pressure of the wash water discharged from thepump.

[0071] Specifically, the heater assembly 92 includes a heater casehaving an inlet port, through which the wash water is introduced, and anoutlet port, through which the wash water is discharged. The water levelsensor 102 is disposed at one side of the heater case in such a mannerthat the water level sensor 102 communicates with the heater case formeasuring the water pressure of wash water passing through the pumpassembly 100 and the heater assembly 102. Consequently, it is determinedwhether the pump is normally operated or not, and the water level of thewash water in the tub 86 is detected.

[0072] Now, a method of controlling wash water circulation for the drumwashing machine with the above-stated construction will be describedwith reference with FIGS. 7 and 8.

[0073]FIG. 8 is a flow chart illustrating a method of controlling a drumwashing machine provided with a wash water-circulating apparatusaccording to the present invention.

[0074] When the washing or rinsing process is initiated, the amount ofclothes is detected, and wash water level is set on the basis of thedetected amount of the clothes, and wash water is supplied up to thewash water level (S1, S2).

[0075] The amount of the clothes is detected on the basis of the reservepower of the motor 90 or how many times the wash water is supplied whilethe clothes are put in the drum 88. The water-supply valve is opened fora prescribed period of time on the basis of the detected amount of theclothes so that the wash water is supplied into the tub 86.

[0076] When the wash water is supplied up to the wash water level, thewashing and rinsing processes are carried out, and simultaneously thepump is operated so that the washing and rinsing efficiencies areimproved (S3, S4). As the motor 90 is operated, the drum 88 is rotatedwith the result that the clothes are lifted by means of vanes and thendropped. In this way, the washing and rinsing processes are carried out.

[0077] When the wash water is supplied into the tub 86 up to the minimumwater level at which the pump can be operated, the pump is operated fora prescribed period of time so that the wash water in the lower part ofthe tub is pumped. The pumped water passes through the pump assembly 100and the heater assembly 92, and is then sprayed into the tub 86 via thecirculation channel 104 so that the clothes become wet.

[0078] The minimum water level of the wash water in the tub at which thepump can be operated is detected by means of the time for which thewater-supply valve is opened.

[0079] When the discharging pressure P of the pump is less than theprescribed pressure P₀ while the pump is operated, wash water is furthersupplied, and simultaneously the pump is stopped (S5, S6, S7). In otherwords, the pump is operated when the wash water is supplied up to thewash water level. Subsequently, the wash water is circulated along thecirculation channel 104 so that the wash water is sprayed to the tub 86,and thus the clothes become wet. As a result, the water level of thewash water is lower than the wash water level, whereby the washing orrinsing efficiency is deteriorated, or the water level of the wash wateris lower than the minimum water level, whereby the operationalreliability of the pump is deteriorated. Consequently, the wash water isfurther supplied for preventing the above-mentioned deterioration of thewashing or rinsing efficiency and the operational reliability of thepump.

[0080] When the pump is operated again, the wash water in the lower partof the tub 86 is pumped. The pumped wash water passes through the pumpassembly 100 and the heater assembly 92, and is then guided along thecirculation channel 104. Consequently, the water pressure P of the washwater is measured by means of the water level sensor 102 mounted at theoutlet of the heater assembly 92.

[0081] As the wash water is supplied into the tub 86 until the waterlevel of the wash water is higher than the minimum water level at whichthe pump can be operated, only the wash water passes through the pumpassembly 100. Consequently, the operational reliability of the pump isimproved, and the water pressure of the wash water, which is measured bymeans of the water level sensor 102, is also accurately measured.

[0082] As the clothes become wet in the tub 86, and simultaneously thepump is operated, the water level of the wash water in the tub 86 islowered. For this reason, wash water is supplied while the pump is notoperated for a prescribed period of time to, whereby the water level ofthe wash water in the tub 86 is prevented from dropping below theminimum water level at which the pump can be operated.

[0083] Even when air is introduced as the pump is operated while thewash water is supplied into the tub 86 below the minimum water level atwhich the pump can be operated, the pump is stopped for the prescribedperiod of time t₀ so that the air introduced into the pump escapes,whereby the operational reliability of the pump is improved when thepump is operated again.

[0084] After the prescribe period of time to expires while the pump isstopped, the pump is operated again (S8, S9). When the time for whichthe pump is stopped is larger than the prescribed period of time t₀while the water is supplied through the opened water-supply valvealthough the pump is stopped, the pump is operated again, whereby thewash water is circulated so that the clothes become wet.

[0085] When the discharging pressure P of the pump is not less than theprescribed pressure P₀ while the pump is operated again, the supply ofthe wash water is stopped (S10, S11). As the clothes become wet in thetub 86, and the pump is operated, the water level of the wash water islowered in the tub 86. When the discharging pressure P of the pump ismore than the prescribed pressure P₀, it is determined that the clothesbecome sufficiently wet, and the wash water is supplied above the washwater level although the wash water is circulated. Consequently, furthersupply of wash water is stopped.

[0086] When the discharging pressure P of the pump is less than theprescribed pressure P₀, however, wash water necessary for the clotheswetting operation and the wash water circulation is supplied while thepump is stopped.

[0087] The above-mentioned steps are repeated so that the wash water issupplied into the tub 86. At this time, it is preferable that the timefor which the pump is stopped is shorter than the time for which thepump is operated.

[0088] In the case that the pump is operated when the water is supplied,the water-supply valve may be closed so that the wash water pumped bymeans of the pump is absorbed into the clothes for a sufficient periodof time.

[0089] Now, a description will be given of the water level based onwater-supplying time and the pump operating condition when the washwater is supplied as mentioned above. As shown in FIG. 9, the pump isoperated while the water is further supplied. As a result, the waterlevel is gradually lowered. After the pump is operated for a requiredperiod of time, the pump is stopped for the prescribed period of time t₀so that the clothes become wet with the wash water, and the airintroduced into the pump escapes.

[0090] The wash water does not pass through the pump assembly 100 andthe heater assembly 92 in the section where the pump is stopped for theprescribed period of time t₀. Consequently, the water level of the washwater measured by means of the water level sensor is rapidly decreased.The wash water passes through the pump assembly 100 and the heaterassembly 92 in the section where the pump is operated again.Consequently, the water level of the wash water measured by means of thewater level sensor is rapidly increased.

[0091] When the water level of the wash water detected by means of thewater level sensor 102 is higher than the prescribed water level afterthe pump is repeatedly stopped and operated again for prescribed timesas described above, the motor 90 is rotated in one direction, and thepump is operated so that the washing and rinsing operations are carriedout.

[0092] As apparent from the above description, the present inventionprovides a wash water-circulating apparatus for washing machines, whichis capable of detecting the water pressure of wash water discharged froma pump assembly operated when the wash water is re-circulated so that itis determined whether a pump is normally operated or not and the washwater supplied into a tub is detected. Consequently, the minimum amountof the wash water necessary for the pump operation is used when thewashing and rinsing processes are carried out, whereby the consumedamount of the wash water is decreased, and the operational reliabilityof the pump is improved.

[0093] According to a preferred embodiment of the present invention, awash water circulation channel is connected to the lower part of the tubsuch that the wash water is sprayed at the lower part of the tub.Consequently, the total length of the circulation channel is relativelyshortened, whereby the consumed amount of the wash water and the flowloss are decreased when the washing and rinsing processes are carriedout, and thus the consumed amount of electric energy based on theoperation of the pump is also decreased.

[0094] According to another preferred embodiment of the presentinvention, a heater assembly is disposed on the circulation channel.Consequently, it is not necessary to supply an excessive amount of thewash water into the tub such that the heater is submerged under thewater in the tub, whereby the consumed amount of the wash water isdecreased and the consumed amount of electric energy is also decreasedwhen the clothes are washed. Furthermore, the heater is submerged underthe wash water when the pump is operated. Consequently, the operationalreliability of the heater is improved.

[0095] With a method of controlling wash water circulation for washingmachines as mentioned above, the wash water is further supplied into thetub, and simultaneously the pump is repeatedly stopped for a prescribedtime while the pump is operated so that air introduced into the pump isdischarged, whereby the operational reliability of the pump is improved.

[0096] Although the preferred embodiments of the present invention havebeen disclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

What is claimed is:
 1. A wash water-circulating apparatus for washingmachines, comprising: a circulation channel connected between one sideof a tub and the other side of the tub for allowing wash water tocirculate therethrough; a pump assembly disposed on the circulationchannel for forcibly circulating the wash water; and a water levelsensor disposed at the pump assembly or on the circulation channeldownstream of the pump assembly for measuring the water pressure of thewash water discharged from the pump assembly.
 2. The apparatus as setforth in claim 1, further comprising a heater assembly disposed on thecirculation channel downstream of the pump assembly for heating thecirculated wash water.
 3. The apparatus as set forth in claim 2, whereinthe water level sensor is mounted on the circulation channel between thepump assembly and the heater assembly.
 4. The apparatus as set forth inclaim 2, wherein the water level sensor is disposed at the heaterassembly.
 5. The apparatus as set forth in claim 2, wherein the waterlevel sensor is disposed on the circulation channel downstream of theheater assembly.
 6. The apparatus as set forth in claim 1, furthercomprising a drainage channel connected to the pump assembly fordischarging the wash water in the tub to the outside, wherein the washwater is selectively pumped to the circulation channel or to thedrainage channel by means of the pump assembly.
 7. The apparatus as setforth in claim 1, wherein the circulation channel has a washwater-spraying end disposed at the lower part of the tub so that thewash water is sprayed into the tub through the wash water-spraying end.8. The apparatus as set forth in claim 1, wherein the circulationchannel has a wash water-spraying end disposed at the upper part of thetub so that the wash water is sprayed into the tub through the washwater-spraying end.
 9. A method of controlling wash water circulationfor washing machines, comprising the steps of: re-circulating wash watersupplied into a tub along a circulation channel by operating a pump; andmeasuring the discharging pressure of the pump while the wash water isre-circulated, and further supplying water into the tub if thedischarging pressure of the pump is less than a prescribed pressure. 10.The method as set forth in claim 9, wherein the pump is stopped for aprescribed period of time when the water is further supplied into thetub.
 11. The method as set forth in claim 9, wherein the pump isperiodically stopped/operated when the water is further supplied intothe tub.
 12. The method as set forth in claim 11, wherein thepump-stopping time is shorter than the pump-operating time.
 13. Themethod as set forth in claim 9, further comprising the steps ofmeasuring the discharging pressure of the pump after the water isfurther supplied, and stopping supply of water if the dischargingpressure of the pump is not less than a prescribed pressure.
 14. Themethod as set forth in claim 13, wherein the pump is stopped for aprescribed period of time when the water is further supplied into thetub.
 15. The method as set forth in claim 13, wherein the pump isperiodically stopped/operated when the water is further supplied intothe tub.
 16. The method as set forth in claim 15, wherein thepump-stopping time is shorter than the pump-operating time.
 17. Awashing machine comprising: a tub for storing wash water; a circulationchannel connected between one side of the tub and the other side of thetub for allowing the wash water to circulate into the tub therethroughso that the wash water is sprayed into the tub; a pump assembly disposedon the circulation channel for forcibly circulating the wash water; awater level sensor for measuring the water pressure of the wash waterdischarged from the pump assembly; and control means for controllingsupply of the wash water into the tub and operation of the pump assemblyon the basis of the signal from the water level sensor.
 18. The machineas set forth in claim 17, further comprising a drainage channelconnected to the pump assembly for discharging the wash water in the tubto the outside, wherein the wash water is selectively pumped to thecirculation channel or to the drainage channel by means of the pumpassembly.
 19. The machine as set forth in claim 17, wherein the machineis a drum washing machine with the tub disposed approximatelyhorizontally.
 20. The machine as set forth in claim 17, wherein themachine is an upright washing machine with the tub disposedapproximately vertically.